This is an interesting thread. There are some interesting things as to HouseGuests that have said they wouldn't do Big Brother again, so my list will take this into consideration.
Big Brother 8
Definites:
Jen -- Big drama causer, and a shoo-in to be asked back. The fact she represented BB8 in the BB10 food challenge shows that she must be regarded at least somewhat highly by the producers.
Eric -- A good strategic player that was hampered by the memorable America's Player twist the first time around. Hosting BB9's opening HoH competition shows the producers like him.
Choose 1 (one) of these 3 (three):
Jessica -- They gave her another try for BB11 so they must want her back in some regard. Fairly popular as well.
Daniele -- All-Stars 2 without a Donato just wouldn't be All-Stars. I read somewhere recently that Dick was "done with BB", so that'd make her a likely choice.
Dick -- He was memorable, that's for sure. Just in case he changes his mind, I'd put him here.
Big Brother 9
Definites:
Chelsia -- Fairly popular player that brought a lot of excitement to the house. Could definitely see her being asked back, and was kind of surprised she wasn't asked to represent the Off-Beats last year.
Pick 1 (one) of 4 (four):
Ryan -- Just a laid-back guy that was pretty popular.
Crazy James -- Wouldn't rule it out since he was popular. Kind of a lousy player though.
Sheila -- An older female, could probably only be in if Renny isn't.
Definitely Not:
Adam or
Matty -- Likely will be incarcerated.
Big Brother 10
Defnites:
Dan -- It's a Summer show, and he's a teacher. He loves the game, is popular, and would probably enjoy being back.
Brian -- Even though he was out early, I could see him being asked back because CBS likes him, and he was popular.
Pick 1 (one) of 2 (two):
Renny -- Only could be asked back if Sheila isn't. Could see her doing it again.
Keesha -- Only if Daniele isn't in I think. She was well liked though, so she has a decent shot.
Big Brother 11
Definites:
Ronnie -- Villains tend to be asked back (Jase, Allison, and Jessie). So evil, loves the game, and would probably give it another shot.
Possible:
Casey -- Funny and well-liked. Even though he was out kind of early, definitely could see him going back.
Russell -- Brings excitement to the house, fairly good player.
Michele -- Had longevity, definitely desperate for attention. Warning: Completely changed since her time on the show.
Kevin -- OK strategic player, really deep in the maybe pile though.
Unlikely:
Jeff or
Jordan -- Jordan said somewhere she was done with Reality TV and Jeff said he'd only do TAR again, not BB.
Big Brother 12
Possible:
Terry -- So far I like the cut of his jib.
Overall:
Eric
Jen
Daniele
Chelsia
Ryan
Dan
Brian
Renny
Ronnie
Casey
BB12
BB12
Any Other